1/* Demo leapsecond deadlock
2 *              by: John Stultz (john.stultz@linaro.org)
3 *              (C) Copyright IBM 2012
4 *              (C) Copyright 2013, 2015 Linaro Limited
5 *              Licensed under the GPL
6 *
7 * This test demonstrates leapsecond deadlock that is possibe
8 * on kernels from 2.6.26 to 3.3.
9 *
10 * WARNING: THIS WILL LIKELY HARDHANG SYSTEMS AND MAY LOSE DATA
11 * RUN AT YOUR OWN RISK!
12 *  To build:
13 *	$ gcc leapcrash.c -o leapcrash -lrt
14 */
15
16
17
18#include <stdio.h>
19#include <stdlib.h>
20#include <time.h>
21#include <sys/time.h>
22#include <sys/timex.h>
23#include <string.h>
24#include <signal.h>
25#ifdef KTEST
26#include "../kselftest.h"
27#else
28static inline int ksft_exit_pass(void)
29{
30	exit(0);
31}
32static inline int ksft_exit_fail(void)
33{
34	exit(1);
35}
36#endif
37
38
39
40/* clear NTP time_status & time_state */
41int clear_time_state(void)
42{
43	struct timex tx;
44	int ret;
45
46	/*
47	 * We have to call adjtime twice here, as kernels
48	 * prior to 6b1859dba01c7 (included in 3.5 and
49	 * -stable), had an issue with the state machine
50	 * and wouldn't clear the STA_INS/DEL flag directly.
51	 */
52	tx.modes = ADJ_STATUS;
53	tx.status = STA_PLL;
54	ret = adjtimex(&tx);
55
56	tx.modes = ADJ_STATUS;
57	tx.status = 0;
58	ret = adjtimex(&tx);
59
60	return ret;
61}
62
63/* Make sure we cleanup on ctrl-c */
64void handler(int unused)
65{
66	clear_time_state();
67	exit(0);
68}
69
70
71int main(void)
72{
73	struct timex tx;
74	struct timespec ts;
75	time_t next_leap;
76	int count = 0;
77
78	setbuf(stdout, NULL);
79
80	signal(SIGINT, handler);
81	signal(SIGKILL, handler);
82	printf("This runs for a few minutes. Press ctrl-c to stop\n");
83
84	clear_time_state();
85
86
87	/* Get the current time */
88	clock_gettime(CLOCK_REALTIME, &ts);
89
90	/* Calculate the next possible leap second 23:59:60 GMT */
91	next_leap = ts.tv_sec;
92	next_leap += 86400 - (next_leap % 86400);
93
94	for (count = 0; count < 20; count++) {
95		struct timeval tv;
96
97
98		/* set the time to 2 seconds before the leap */
99		tv.tv_sec = next_leap - 2;
100		tv.tv_usec = 0;
101		if (settimeofday(&tv, NULL)) {
102			printf("Error: You're likely not running with proper (ie: root) permissions\n");
103			return ksft_exit_fail();
104		}
105		tx.modes = 0;
106		adjtimex(&tx);
107
108		/* hammer on adjtime w/ STA_INS */
109		while (tx.time.tv_sec < next_leap + 1) {
110			/* Set the leap second insert flag */
111			tx.modes = ADJ_STATUS;
112			tx.status = STA_INS;
113			adjtimex(&tx);
114		}
115		clear_time_state();
116		printf(".");
117	}
118	printf("[OK]\n");
119	return ksft_exit_pass();
120}
121